Methods of Water Treatment

Today, people are becoming more aware of the importance to drinking water, with that awareness comes the concern about the quality of water they are drinking, water that looks drinkable can contain harmful substances that may cause illness if ingested. Communities get their water from rivers and lakes (surface water), from springs and wells (groundwater) or from both surface and ground, these sources of fresh water makes up less than 1% of the total water resources on earth. About 97% of the water on earth is found in the oceans. Most of the rest is frozen in the polar ice caps and in glaciers.

Water purification is a process of removing harmful substances and odor from a raw water source .Water that looks drinkable can contain harmful substances that may cause illness if ingested.Surface water may be polluted by sewage, industrial wastes, or dead plants and animals. Groundwater may be polluted by leaks from sewage or industrial wastes. Both surface water and groundwater may also contain other solids and may have objectionable tastes and odors.

Methods of Water Treatment:

• Intake Filtering - in this method raw or untreated water usually enters a water-treatment plant through a pipeline or tunnel. A series of screens prevents debris from entering the water-treatment system.

• Chemical Treatment - in this method the raw water is pumped into a discharge basin and then given several types of chemical treatment. Disinfectants like chlorine, chlorine dioxide, iodine, or ozone are added in controlled amounts to kill bacteria and other organisms. When chlorine is used, activated carbon or ammonia is usually also added to remove the taste of chlorine from the water. Fluorides are sometimes added to the water to help prevent tooth decay.

• Water containing calcium or magnesium (hard water) is treated to remove these minerals, this process is called water softening. To prevent the corrosion of pipes, lime or caustic soda is sometimes added to acidic water.

• Sedimentation - this method is often used as a first stage in modern waste water treatment plant. This process consists of allowing matter suspended in the water to settle. Coagulant like aluminum sulfate is added to the water to speed up the sedimentation process by causing small particles to cling together, forming clumps called floc. Water that has been treated with coagulant is gently stirred in a mixing basin before it passes into settling basin. The stirring promotes the formation of the floc. In the settling basin, the water flows slowly and the froc gradually settles forming sludge (thick mud) at the bottom of the basin.
• Filtration - after separating most floc, the water is filtered as the final step to remove remaining suspended particles, water passes on to filter beds. They are usually made up of a layer of gravel 18 to 24 inches (45 to 60 cm) thick covered with sand or crushed anthracite in a layer 24 to 30 inches (60 to 75 cm) thick. As the water drains, the filter trap remaining particles suspended in the water. Drains carry the filtered water to a reservoir. To clean the filter beds, water is passed quickly upward through the filter from below (opposite of the normal direction) with filtered water to remove embedded particles. The wash water is then removed through special drains.
• Aeration - this is done either before or after filtration, the water may be aerated (exposed to the air) to remove unpleasant odors and tastes caused by decomposing organic matters, industrial wastes and some gases. It is also effective in removing radon (gaseous element formed by the radioactive decay of radium) from water. In the process, oxygen in the air combines with foul-smelling substances to change them into odorless compounds.